Codec.Not only Panasonic is typically using higher bitrates (can't exactly figure the numbers though) but they use a higher h.264 profile (5.0) which means their encoder is using more advanced features and thus getting even more IQ for the bitrate they use.

Peaking & Zebras. This I can't be sure but I believe I've read around that Panasonics have a lot more customization room for both these modes than Olympus (which I suspect doesn't even feature a zebra mode).

Audio monitoring. Another one I'm not familiar on the Olympus, but I believe you have no way to do audio monitoring in-camera, while you have a stereo audio levels graph displayed on the Pannys.

Now this isn't just a Panasonic party:

Stabilization. Olympus IBIS will effectively stabilize every lens that can be mounted on the camera. This is a serious advantage when you can't afford equivalent stabilized lenses, when the lenses in question aren't just stabilized to begin with and when you don't want to be bothered or just can't have the option to use a stabilization rig. Pro's will rebate that argument because they have the camera on a tripod 80% of the time, but I believe it's Olympus only clear and solid win in the video game.

Focus. Kind of a tie. Even though focus is already at a high level on most Panasonics (the GH4 is reported to excel at this) the E-M1 has on-sensor phase detection and this might give it some edge in some kind of situations (like sports). Pro's will rebate that argument because they'll focus manually 95% of the time (and that's why peaking might switch the tables).

Unknown variable:

Rolling shutter. I just don't know how each brand's sensor is placed in this field, however I know that Panasonic has doubled the readout speed (and thus cut RS in half) in their latest batch of sensors (GX7 and forward I believe, even though I might be wrong). Yet this might be a minor detail because you really need to be panning like mad to feel the effect, and if you are panning like mad, the chances are your video will be have bigger problems than RS.

For these reasons, especially 1,2 &3 (for Panasonic) I believe it's really a no brainer if you have a minor interest in video, since the Olympus advantages can always be dealt with through additional hardware if the demand is justifiable.